That's what's nice about TIG. You can use a low amperage (20A in this case) to get the job done locally without heating up the rest of the barrel. I did it in stitches while the threads and chamber remained cool/warm to the touch. Of course it's impossible to exactly match the cooling conditions of the original steel so it will be slightly different...but not remotely enough to worry about...especially in a 9x19mm chambering. I agree with the previous poster that one might start getting concerned about things with a high pressure round, and especially if more invasive work was required. Once again, running the numbers, even the reduced chamber diameter (pre-sleeve) was plenty thick to handle a hot 9mm and then some. This barrel should hopefully last through anything short of the previous owner's screwup.
I can't wait for the heavier spring and buffer to show up this weekend so I can try it out